Diabetes Testing

Vitamin D Testing

Vitamin D testing has been in the news lately. But the mainstream press covered only the bad news. You would have to read the medical press to learn about better choices.

The country’s largest medical laboratory, Quest Diagnostics, just sent out thousands of letter to doctors who ordered Vitamin D tests for their patients. The letters say that results of their Vitamin D tests during the past two years are “questionable.” Quest’s screw up could mean that thousands of people aren’t taking vitamin D supplements when they should.

Testing our levels of vitamin D has surged recently because of studies suggesting that too little can raise the risk of all sorts of complications. More and more recent studies link a vitamin D deficiency to diabetes. Other studies link it to bone weakness, cancer, heart attacks, and other illnesses.

The possibly defective Quest test often costs unsuspecting people as much as $200 and required them to make a trip to their hospital. But now much less expensive and more convenient alternatives are here.

Obviously, no one can tell us yet whether their accuracy could be an issue as it was with Quest. But the test I like best — and just bought for myself — comes from a nonprofit organization with some of the biggest names in the field behind it.

This organization is GrassrootsHealth in Encinitas, California, and they call the program “D*Action.” Its many sponsors include most of the big names in the field, including Anthony W. Norman, PhD, at the University of California, Riverside (my alma mater). His laboratory discovered the active form of vitamin D in 1971.

Seventeen other University of California scientists are part of the consortium. Dr. John Cannell, the executive director of the nonprofit Vitamin D Council, which has done so much to educate me and others about the value of greater vitamin D supplementation, is a member of the National Scientists Panel supporting GrassrootsHealth.

So too is John Hathcock, PhD, of the Council for Responsible Nutrition, who marshaled the evidence for much greater supplementation in the January 2007 issue of The American Journal of Clinical Nutrition. That was the basis of my earlier article here, “How Much Vitamin D?” and my personal decision to increase my vitamin D intake to 10,000 IU every day.

Another member of the panel is Dr. Walter C. Willett, of Harvard University’s school of public health. Dr. Willett is the country’s most influential epidemiologist. He also invented the concept of the glycemic load.

Dr. Joe Prendergast, an innovative endocrinologist who practices in Palo Alto, California — and who also wrote the forward to my most recent book, Losing Weight with Your Diabetes Medication — brought the GrassrootsHealth vitamin D test to my attention in a recent issue of his “Diabetes Newsletter.”

Unlike the expensive and possibly inaccurate Quest test, the GrassrootsHealth test is only $30 and a quick health survey. They sent me a vitamin D blood spot test just a couple of days after I ordered it online. It’s available to be used at home — except for a reason I don’t understand in New York state. I just mailed it back to them and expect my results in a few days.

Then, I will see if I am getting too little or too much vitamin D and adjust it accordingly. So, what should our levels be?

Sue Penckofer, PhD, RN, of the Niehoff School of Nursing in Chicago, and three of her associates addressed this question in their recent review, “Vitamin D and Diabetes,” in The Diabetes Educator. The abstract of their article is online, and Dr. Penckofer kindly sent me the full-text PDF.

The normal vitamin D level is 30 to 60 ng/ml, that article states (GrassrootsHealth puts the recommended level as 40 to 60 ng/ml). But many people with diabetes have much less vitamin D in their systems.

The article in The Diabetes Educator goes on to review the many links between vitamin D deficiency and type 1 and type 2 diabetes, the metabolic syndrome, and diabetic neuropathy. “The reasons for this include diet, lack of sun exposure, obesity, renal impairment, and genetic predisposition,” the article says. “It appears that diet alone will not provide sufficient amounts of vitamin D, and that treatment with supplements is probably necessary for most individuals with diabetes.”

Since I have taken about 10,000 IU of vitamin D for a couple of years, you might think that I would have no reason for concern. But I don’t know.

I’m confident that I am not taking too much vitamin D. “You cannot take too much — unless you are taking extra calcium,” Dr. Joe wrote me. “The extra calcium is what gave mega-doses of Vitamin D a bad name. I have never seen a paper on vitamin D toxicity.”

“Your body handles increasing levels of Vitamin D without problems,” Dr. Joe says. “The values in the blood go up increasingly as you take higher levels of Vitamin D. When all the sites are saturated, the body will not allow any more Vitamin D in, and the blood levels begin to fall.”

So now I wonder if my level is high enough even with all that I’m taking. That’s why the GrassrootsHealth people are testing my vitamin D level.

This article is based on an earlier version of my article published by HealthCentral.

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  • Carole Gonzalez at

    OK Thank you David. I just signed up and will get tested just to see how effective that 8,000 per day has been. I will let you know.